HEARING (AUDITION) AND BALANCE

Hearingor audition is the sense of soundperception and results from tiny hair fibers in the inner ear
detecting the motion of a membrane which vibrates in response to changes in the pressure
exerted by atmospheric particles within (at best) a range of 20 to 20000 Hz. Sound can also
be detected as vibrations conducted through the body by tactician. Lower and higher
frequencies than can be heard are detected thisway only. The main features regarding ear are:

•  Ear is regarded as the organ of hearing.
•  Like our other senses, our hearing or audition, is highly adaptive
•  Sense of motion and balance is regarded as the main and important function of the ear
•  Organisms have the ability to hear a wide range of sounds with different frequencies (ranging from
higher to very low faint voice)__ but more importantly we can easily detect different voices of people whom we know or met
•  For this, the important question is how we do it? How the transformation of sound waves into
neural messages takes place?

Some Interesting Facts about Hearing 
•  Animals have the capability of hearing more sounds than humans
•  Dolphins have the best sense of hearing among all animals
•  When people go up high in the mountains, the changes in pressure cause the ear to pop
•  Babies can get ear aches because of the milk deposit in the eustachian tube, which helps the
bacteria to grow there and may cause problems later in life
•  Children can hear more noises than adults, as their ears are more sensitive than that of adults
•  Ear aches result when too muchfluid causes pressure in the eardrum__ often occur due to
allergies, virus or some sort of infection

The Human Ear: Anatomy/ Structure
The primary apparatus of hearing i.e., the ear is divided into three parts
1.  The outer ear
2.  The middle ear
3.  The inner ear

1. The Outer Ear 
•  The outer ear serves the function of collecting the sound waves from the environment to the
internal portions of the ear. It is shaped like a reverse megaphone
•  It also plays an important role in locating the sound direction from which it originates

Auditory Canal 
•  When sound waves originate from the vibrating object, they then pass through the auditory canal,
which is a tube like passage through which the sound travels to the inner part of the ear or “ the
eardrum”.

Eardrum 
•  The part of the ear that starts vibrating when sound waves strike/ hit it.
•  Its intensity of vibration is dependent on how intense the sound waves are___ the more intense the
sound, the more intensely it vibrates.
•  These vibrations are then transmitted to the “ middle ear”.

2. Middle Ear
•  A tiny chamber between the eardrum and cochlea containing three bones---- the hammer, the anvil, and
the stirrup, which transmit vibrations to the oval window.
•  These three bones have only one function, i.e. to convey/ transmit the message to the inner ear.
These bones are also effective in the sense that they strengthen the stimulus (vibration) so that it can be
easily heard. Information (Vibration) Travels Through These Three Bones

Hammer  Anvil  Stirrup   Oval window

Oval Window 

• A membrane between the middle and the inner ear that increases the strength of the stimulus (vibration)
while transmitting them.
• Serves as the amplifier so that tiny or hiss voices could be heard, which otherwise may remain unnoticed.

3. Inner Ear 
•  The innermost region/ part of the ear that contains important structures such as cochlea, semi
circular canals and vestibular sacs, and that changes/ transforms the sound waves into the neural
impulse.
•  Organs that are present in it help us to determine in locating our position and how we are moving
in space.
•  In the inner ear, the sound enters into the cochlea___ a coiled, bony tube filled with the fluid that
receives information (sound) from the oval windowor through bone conduction. The sound waves
that reach here help in triggering the nerve impulse. Basal Membrane
•  Inside the cochlea is the basal membrane passing from the middle of cochlea___ a structure that
divides the cochlea into the upper and lower chambers/ parts.
•  This basal membrane is covered/ surrounded by the tiny hair cells that are bent on the vibration, so
that neural message reaches the brain without any hindrance or difficulty; helps to transmit
information to the temporal lobe’s auditory region.

Sound and Its Physical and Psychological Aspects and Impacts

•  Sound is the primary stimulus for hearing.
•  Sound actually refers to the physical movement of air molecules in regular and wave like pattern/
sequence.
•  When an object creates/ produces sound, it results in the back and forth vibration of its surface,
creating sound waves in the surrounding air. These dense and thin sound waves serve as the
stimulus for the ear/ for hearing process.
•  Sound waves that are being produced differ in their intensity, amplitude, frequency and
complexity___ they afterwards produce corresponding dimensions of sound. i.e. pitch, volume and

timbre.

Frequency 
•  Frequency is the prominent feature/ characteristic of sound and refers to the number of complete
wave lengths/ crests that occur or pass a point in each second.
•  In low frequency of sounds, there are relatively fewer and slower up- and- down wave patterns per
second__ these low frequencies are then translated in what is called “ pitch”.

Pitch 
•  Primarily related with the frequency and refers to the quality of sound that is being produced by the
frequency of the sound wave; expressed in cycles per second__ the trait that makes the sound
“high” or “ low”.
•  The lowest and highest frequencies that humanscan hear range from 20 cycles per second to
20,000 cycles per second.

Volume/ Intensity/ Loudness 
•  Volume or loudness can be described as “ strong” or “ weak”__ determined by the amount of
pressure difference between the compressed partof the sound wave and the prominent part
•  Waves that have low peaks create soft sound as compared tothe waves with higher peaks
•  The range within which humans can hear is extensive measured in unit called decibel (db).
•  If the sound exceeds 120 decibels thenit become painful to human ear.

Timbre 
•  When fundamental tones are combined with the weaker tones, they are then to be known as over tones.
•  Partials and harmonic tones are the audible tones that help to make up timbre__ quality of sound determined by the complexity of sound waves
•  The difference in quality or timbre is determined by the complexity and arrangements of the
overtones that any instrument/ object produces which largely depends on its design and material from which it is made.